Insulation machining in a cable joint

ABSTRACT

A method for improving the properties of a joint between two cable ends having obtaining two cable ends, having uncovered conductors being joined in a connection zone, each cable end also including an uncovered insulation zone including uncovered insulation formed as a cone adjacent the uncovered conductor, covering the conductors with an additional insulation layer, measuring the additional insulation layer and the cones, determining the geometry of the cones and the additional insulation layer based on the measurements, determining a deviation of the geometry from a desired geometry of the cones and the additional insulation layer, where the desired geometry includes a smooth transition between two zones, determining, based on the deviation determination, material to be removed from the cones and the additional insulation layer achieving the desired geometry, and removing the material from the cones and the additional insulation layer.

TECHNICAL FIELD

The invention relates to electric cables, for instance in relation tohigh voltages. More particularly, the invention relates to a method,arrangement and computer program product for improving the properties ofa joint between two cable ends.

BACKGROUND

The forming of joints between cable ends is today a more or less manualexercise where the jointing is performed in armoring or assemblymachines.

One example of a machine that may be used in the forming of a joint isshown WO 2011/127978. In the machine described in this document a cableis received and held in a fixture. A tool is then used for removingmaterial of the cable in order to obtain a smooth transition between ashielding layer and an insulating layer.

Although the document provides some improvements in the forming of ajoint, it would be of interest to improve on the obtaining of the jointeven further, so that the preparation time is reduced and the quality isimproved.

Aspects of the invention are concerned with improvements in relation tothe above-described interfaces.

SUMMARY

One object of the invention is therefore to improve the way a joint isobtained.

This is according to a first aspect achieved through a method forimproving the properties of a joint between two cable ends, the methodbeing at least partly performed by a robot controlled by robotcontroller and comprising:

obtaining two cable ends, the conductors of which are uncovered andjoined in a connection zone, each cable end also comprising an uncoveredinsulation zone comprising uncovered insulation formed as a coneadjacent the uncovered conductor,

covering the joined conductors with a layer of additional insulation,

measuring the layer of additional insulation and the cones,

determining the geometry of the cones and the layer of additionalinsulation based on the measurements,

determining a deviation of the geometry from a desired geometry of thecones and the layer of additional insulation, where the desired geometrycomprises a smooth transition from the uncovered insulation zones to theconnection zone,

determining, based on the deviation determination, material to beremoved from the cones and the layer of additional insulation achievingthe desired geometry, and

removing the material from the cones and the additional layer ofinsulation in order to obtain a joint with improved properties.

The object is according to a second aspect achieved through anarrangement for improving the properties of a joint between two cableends, the arrangement comprising:

a robot with a robot controller, the robot controller being configuredto,

control the robot to obtain two cable ends, the conductors of which areuncovered and joined in a connection zone, each cable end alsocomprising an uncovered insulation zone comprising uncovered insulationformed as a cone adjacent the uncovered conductor,

control the robot to cover the joined conductors with a layer ofadditional insulation,

control the robot to measure the layer of additional insulation and thecones,

determine the geometry of cones and the layer of additional insulationbased on the measurements,

determine a deviation of the geometry from a desired geometry of thecones and the layer of additional insulation, where the desired geometrycomprises a smooth transition from the uncovered insulation zones to theconnection zone,

determining, based on the deviation determination, material to beremoved from the cones and the layer of additional insulation achievingthe desired geometry, and

control the robot to remove the material from the cones and theadditional layer of insulation in order to obtain a joint with improvedproperties.

The object is according to a third aspect achieved through a computerprogram product for improving the properties of a joint between twocable ends, the computer program product comprising computer programcode which when run in a robot controller for a robot, causes the robotcontroller to:

control the robot to obtain two cable ends, the conductors of which areuncovered and joined in a connection zone, each cable end alsocomprising an uncovered insulation zone comprising uncovered insulationformed as a cone adjacent the uncovered conductor,

control the robot to cover the joined conductors with a layer ofadditional insulation,

control the robot to measure the layer of additional insulation and thecones,

determine the geometry of the cones and the layer of additionalinsulation based on the measurements,

determine a deviation of the geometry from a desired geometry of thecones and the layer of additional insulation, where the desired geometrycomprises a smooth transition from the uncovered insulation zones to theconnection zone,

determine, based on the deviation determination, material to be removedfrom the cones and the layer of additional insulation achieving thedesired geometry, and

control the robot to remove the material from the cones and theadditional layer of insulation in order to obtain a joint with improvedproperties.

The invention according to the above mentioned aspects has a number ofadvantages. It allows a desired geometry to be obtained in a precise waywhere there are smooth transitions between the cones and the layer ofadditional insulation. Thereby the electric fields will be smooth andthe reliability of the joint increased. Moreover, the production is fastsince the one and the same robot may be used for the differentoperations. There is thereby no need for moving the cables betweendiffered machines.

In a first variation of the first and second aspects, the geometries ofboth cones are considered in the determining of material to be removedfor obtaining a smooth transition from one uncovered insulation zone tothe connection zone.

It is possible that the desired geometry comprises an angle between thecone surface and a longitudinal axis (A) through the conductor.

In a second variation of the first aspect, the removal of material is aremoval that retains the angle.

In a corresponding second variation of the second aspect, the robotcontroller, when controlling the robot to remove material is furtherconfigured to control the robot to retain the angle during the removal.

It is furthermore possible that in the desired geometry each cone has awall with a thickness that decreases towards the connection zone and, inan uncovered insulation zone, the thickness of the cone wall closest tothe connection zone is the same as the thickness of the additional layerof insulation at the point where it is closest to said uncoveredinsulation zone.

The desired geometry comprises a smooth surface of the cones and theadditional layer of insulation.

In a further variation of the first aspect, the removing of material mayin this case be a removing of material lowering the level of the surfaceso that holes disappear.

In a corresponding further variation of the second aspect the robotcontroller when controlling the robot to remove material is furtherconfigured to control the robot to lower the level of the surface sothat holes disappear.

As yet another alternative it is possible that the desired geometrycomprises corrugations on the cones and/or the layer of additionalinsulation.

In yet another variation of the first aspect, the method furthercomprises applying secondary insulation around the additional insulationand cone to a level that is aligned with the surface of the cone whereits wall is thickest.

In a corresponding variation of the second aspect, the robot controlleris further configured to control the robot to apply secondary insulationaround the additional insulation and cone to a level that is alignedwith the surface of the cone where its wall is thickest.

In still another variation of the first aspect, the obtaining of twocable ends comprises, prior to the covering of the uncovered joinedconductors with a layer of additional insulation, connecting theuncovered conductors to each other and forming the insulation conesadjacent the connection zone.

In a corresponding variation of the second aspect, when obtaining thetwo cable ends, the robot controller is further configured to controlthe robot to, prior to the covering of the uncovered joined conductorswith a layer of additional insulation, connect the uncovered conductorsto each other and form the insulation cones adjacent the connectionzone.

It should be emphasized that the term “comprises/comprising” when usedin this specification is taken to specify the presence of statedfeatures, integers, steps or components, but does not preclude thepresence or addition of one or more other features, integers, steps,components or groups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail in relation to theenclosed drawings, in which:

FIG. 1 schematically shows a perspective view of an end of a highvoltage DC cable,

FIG. 2 is a schematic flow scheme of a number of method steps used inthe forming of a joint between two cable ends,

FIG. 3 schematically shows the forming of a connection between theconductors of the joint in a connecting zone using a robot beingcontrolled by a robot controller,

FIG. 4 schematically shows the forming of insulation cones around theconnecting zone using the robot,

FIG. 5 schematically shows the forming of an additional insulation layerin the connection zone using the robot,

FIG. 6 schematically shows a number of measurement points on theinsulation cones and the additional insulation layer in the connectingzone for measuring the cones and additional insulation layer,

FIG. 7 schematically shows removal of material from of a cone forobtaining a desired geometry of the cones and additional insulationlayer, and

FIG. 8 schematically shows the adding of further insulation above thecones and additional insulation layer, and

FIG. 9 shows a computer program product in the form of a CD ROM discwith a computer program performing the functionality of the control unitof the remote control device.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and notlimitation, specific details are set forth such as particulararchitectures, interfaces, techniques, etc. in order to provide athorough understanding of the invention. However, it will be apparent tothose skilled in the art that the invention may be practiced in otherembodiments that depart from these specific details. In other instances,detailed descriptions of well-known devices, circuits and methods areomitted so as not to obscure the description of the invention withunnecessary detail.

The invention is generally directed towards an electric cable such as aDirect Current (DC) cable like a High Voltage Direct Current (HVDC)cable, for instance operated at 100 kV and above. It should here berealized that the invention is not limited to these types of electriccables, but may also be used in relation to for instance AlternatingCurrent (AC) cables and for cables at other voltage levels. Theinvention is more particularly concerned with the forming of a jointbetween two such cables, which joint may as an example be a so-calledfactory joint.

FIG. 1 schematically shows an end portion 24 of a first such DC cable 22that is to be joined with a corresponding end of a similar second DCcable. The cable is an insulated electric high voltage DC cable 22 andcomprises from inside and out: a high voltage DC conductor 10, a polymerbased insulation system 12-16, a grounding layer 18, and an outercovering or sheath 20. In this example the insulating system comprises afirst insulating layer inside a second insulating layer 14 and a thirdinsulating layer 16 outside of the second insulating layer 14. The firstinsulating layer 12 may be a first semiconductive insulating layer, thesecond insulating layer 14 may be a main insulating layer and the thirdinsulating layer 16 may be a second semiconductive insulating layer. Itshould here also be realized that the third layer, i.e., the secondsemiconductive insulating layer may be omitted.

The polymer based insulation system 12-16 may be extruded, molded, ormanufactured in any convenient manner. The main insulating layer 14 maybe a crosslinked polyethylene layer, a thermoplastic layer, or a layerof other suitable material.

As was mentioned above the invention is concerned with forming a jointbetween two such cable ends.

FIG. 2 shows a number of method steps used in the forming of a jointbetween two cable ends, where at least some of the steps are beingperformed by a robot under the control of a robot controller in a methodof improving the properties of a joint between two cable ends.

The operations performed on the cables by the robot are thus controlledby a robot controller, which also performs calculations in relation toat least some of these operations. This combination of robot and robotcontroller also forms an arrangement for improving the properties of ajoint between two cable ends.

In order to obtain the joint it may be necessary to remove the abovementioned grounding layer 18 and sheath 20 from the cable end 24 forobtaining a connection zone in which a connection between the twoconductors 10 of two cables are to be made. In order to obtain theconnection zone it may also be necessary to remove the insulatingsystem, i.e., the first and second semiconductive insulation layers 12and 16 and the main insulating layer 14. Such removal may be performedby the robot using a cutting tool (not shown). Here it may also bementioned that it is possible that more of the sheath, grounding andsecond semiconductive insulation layers may be removed than the firstsemiconductive insulation layer and the main insulation layer, so thatthis first semiconductive insulation and main insulation layers mayextend beyond the edge of the sheath, grounding layer and the secondsemiconductive layer. Thereby each cable may comprise a part of theconnection zone, such as half of the connection zone and an uncoveredinsulation zone, i.e., a zone where insulation is uncovered and in thiscase where the second layer of insulation is uncovered. This uncoveredinsulation zone is also neighboring the uncovered conductor. Theuncovered insulation zone may thus be placed adjacent the connectionzone. The connection zone thus comprises the uncovered conductors of thetwo cable ends and this connection zone is surrounded by two uncoveredinsulation zones, which in turn transition into the non-tampered part ofthe cable where no layer removal has been made.

FIG. 3 schematically shows the robot 42 with robot controller 46handling the jointing of the cables, where there is a connection zone CZwith the uncovered conductors 10 of two cables that are to be connectedand the connection zone CZ is surrounded by a first and a seconduncovered insulation zone UIZ1 and UIZ2 with remaining firstsemiconductive insulation 12 and main insulation 14 but removed secondsemiconductive insulation 16, ground layer 18 and sheath 20. In theuncovered insulation zone, the insulation has been uncovered so that itmay be exposed to air. In this case it can be seen that the maininsulation layer 14 is exposed to air. The first and second uncoveredinsulation zones UIZ1 and UIZ2 thereafter transitions into unaltered ornon-tampered cable sections, i.e., cable sections without material beingremoved.

It may here be mentioned that the robot 42 as well as the sections andlayers and are not to scale.

After the layers have been removed in the above described way from theuncovered insulation zones UIZ1 and UIZ2, and when all material exceptthe conductors have been removed from the connection zone CZ, i.e., onlythe conductors 10 remain in this zone CZ, the robot 42 connects theseconductors, step 26. This is schematically illustrated in FIG. 3 . Forthis purpose the robot 42 may be equipped with a first tool 44 forconnecting the conductors 10 with each other. The connecting tool maywith advantage be a welding tool used to weld the two conductors to eachother, where the welding may as an example be Tungsten Inert Gas (TIG)or Metal Inert Gas (MIG) welding.

Thereafter follows the forming of insulation cones, which cones may betruncated cones. The cones may be obtained through shaping the secondinsulation layer 14 in the uncovered insulation zones UIZ1 and UIZ2 intothe shape of a cone 50, step 28. This shaping is schematically shown inFIG. 4 . For this reason the robot 42 may be equipped with a second tool48 that is used to cut and/or smooth the surface of the main insulationlayer 14 into the shape of a cone 50. This type of shaping is made inthe uncovered insulation zone on both cable ends. A cone can also beseen as being provided with a wall having a thickness that diminishes ordecreases towards the connection zone CZ.

It can thus be seen that two cable ends have been obtained where theconductors are uncovered and connected in the connection zone CZ andwhere the cable ends each also comprises an uncovered insulation zoneUIZ1 and UIZ2 comprising uncovered insulation 14 formed as a cone 50neighboring or adjacent the uncovered conductor 10 in the connectionzone CZ.

After the above mentioned measured have been performed, it is thennecessary to place additional insulation around the joined conductors inthe connection zone CZ, step 30.

The placing of additional insulation 52 may involve placing additionalinsulation of the same type as was used in the first insulating layer ofthe cable. This means that in the present example, the additionalinsulation 52 would be semiconductive insulation that is placed in theconnection zone CZ around the joined conductors 10. This isschematically shown in FIG. 5 . The placing may be carried out throughthe robot 42 employing a third tool 54 that winds sheets of additionalinsulation around the joined conductors, such as winding sheets ofcellulose or polymer paper comprising carbon black particles around theconductors-. The layer 52 of additional insulation material therebyobtained is here provided in a thickness that is roughly equivalent tothe inner diameter of the cone 54. The application may in this case notbe exact.

Thereafter the robot 42 uses a fourth tool 56, which may comprise anultrasonic sensor, in order to measure the additional insulation layerand the cone, step 32, which measuring may involve measuring thethickness of the additional insulation layer 52 in the connection zoneCZ as well as thickness of the cones 50 in the uncovered insulationzones UIZ1 and UIZ2, step 32. There may because of this be defined anumber of measurement points MP along the surface of the cones 50 andthe surface of the additional insulation 52. The measurement points MPmay more particularly be provided radially around as well as axiallyalong a longitudinal axis A defined by the conductors 10 of the joint.

A measurement point may as an example be defined on the surface of acone 50 at an axial position along the longitudinal axis A. A number ofmeasurement points of the cone surface surrounding the axis at the sameaxial position may become a set of measurement points. The points may inthis case follow a curve defined by the shape of the cone, such as acircle, which curve may be provided in a plane that is perpendicular tothe axis A. A number of such sets of measurement points may then bedefined on the surfaces of the cones 50 along the axis A in the firstand second uncovered insulation zones UIZ1 and UIZ2 as well as on thesurface of the additional insulation layer 52 in the connection zone CZ.The surfaces are in this case the outer surfaces, i.e., the surfacesfacing away from the axis A.

The measurements may be made through the robot 42 moving the tool 56between measurement points. As an alternative it is possible that therobot is moved axially between the two uncovered insulation zones UIZ1,UIZ2 while the cable ends 24 are being rotated by a machine.

Based on the measurements obtained from the measurement points MP, therobot controller 46 then forms a model of the geometry of the cones 50in the uncovered insulation zones UIZ1, and UIZ2 and the additionalinsulation layer in the connection zone CZ, step 33.

The robot controller 46 may therefore determine the shapes of the conesand the additional insulation layer as well as the thicknesses of thecone walls and additional insulation layer. It may also detect anyprotrusions or holes in the outer surface of the cones and theadditional insulation layer.

Based on the information from the measurements, the robot controller 46thus builds a model, such as three-dimensional model of the cones andadditional insulation in which models the shapes, including any surfaceirregularities, and thicknesses of theses element are defined.

The robot controller 46 may thereafter determines a deviation of themodel geometry from a desired geometry of the cones and layer ofadditional insulation, step 34, where the desired geometry comprises asmooth transition from the uncovered insulation zones to the connectionzone.

A desired geometry may be a geometry where protrusions and holes havebeen removed from the surfaces of the cones and additional insulationlayer. It may additionally be the achieving of a desired surfacequality, which desired surface quality may be that the surface issmooth. As an alternative a desired surface quality may be a surface ofthe cones and/or the additional insulation layer having corrugations.

A desired cone geometry may comprise a desired cone shape and a desiredshape of the additional insulation. A desired cone shape may be based onusing a desired angle of inclination a of the outer surface of a cone 50to the longitudinal axis A defined by the conductor 10. Also theadditional insulation may have a desired shape relating to an angle ofinclination. However, in this case the desired angle of inclination iszero as the outer surface is parallel with the axis A. A desired shapeof the additional insulating layer may be a cylinder shape with adesired thickness. A desired cone shape may comprise a smooth surface ora corrugated surface at the desired angle of inclination and a desiredshape of the additional insulation may also comprise a smooth orcorrugated surface.

A cone may have a nominal shape defined by the above-mentioned anglesand the measurements being made in an uncovered insulation zone may leadto deviations of the cone surface from this shape through the occurrenceof protrusions and holes. It is in the same way possible that themeasurements being made of the additional insulation layer may lead todeviations of the measured insulation layer surface from the desiredinsulation layer surface shape through the occurrence of protrusions andholes.

Another possible deviation is that the desired surfaces are to comprisecorrugations, while the surfaces of the model do not.

Thereafter the robot controller 46 determines material to be removedfrom the cones 50 and the additional insulating layer 52 that achievesthe desired geometry based on the deviation determination, step 35.

The determination may therefore involve a determination of material tobe removed that achieves the desired cone shape and additionalinsulation shape.

If the desired shapes comprise smooth surfaces then this may be achievedthrough removing material to a level below the surface of the modelwhere no holes remain. This removal may then also be made whileretaining the same angle of inclination. The determination may thus be adetermination of amount of removal of material from a cone 50 thatretains the angle α while providing a smooth cone surface together withremoval of material from the semiconductive insulation layer 52 thatmakes the radial surface of the semiconductive insulation layer smooth.

In another variation, holes and protrusions are still removed, while atthe same time introducing corrugations.

Moreover as one aspect of the desired geometry is that there should be asmooth or seamless transition from the uncovered insulation zones to theconnection zone, i.e., that there is a seamless transition from a cone50 to the additional insulation layer 52, the edge of a cone 50 adjacentthe connection zone CZ has to be flush with the outer periphery of thesemiconductive insulation layer 52 of the connection zone CZ. The edgeof the outer surface of the cone 50 in an uncovered insulation zone UIZ1or UIZ2 being closest to the connection zone CZ thus has to be flushwith the outer surface of the additional insulation layer 52. This meansthat the core surface at this edge, is to have the same radial distanceto the longitudinal axis A as the additional insulation layer 52 Thiscondition is required for both cones. Put differently, it can be seenthat in an uncovered insulation zone the thickness of the cone wallclosest to the connection zone CZ is the same as the thickness of theadditional insulation layer at the point where it is closest to thisuncovered insulation zone.

In the case of obtaining a smooth surface, this means that if the amountof material needed to be removed from a cone 50 while retaining theprofile leads to the part of the outer surface of a cone that is closestto the connection zone CZ having a first distance to the axis A and thedetermination of the amount of material needed to be removed from theconnection zone CZ leads to the outer surface of the additionalinsulating layer 52 having a second distance to the longitudinal axis,then more material has to be removed from the additional insulatinglayer 52 if the second distance is higher than the first distance, eventhough a material removal corresponding to the second distance issufficient for obtaining a smooth surface. In an analogous manner morematerial has to be removed from the cone, while retaining the desiredangle if the first distance is longer than the second distance.

As this consideration has to be made for both cones, the considerationmade above regarding the first and second distances associated with onecone and the additional insulation layer 52 has to at the same timeinclude a consideration of a third distance of a second conecorresponding to the first distance. The element having the lowestdistance to the axis A, such as one of the cones or the additionalinsulation layer, is then decisive for the determination of material tobe removed also from the other elements. It can thereby also be seenthat the geometries of both cones are considered in the determining ofmaterial to be removed for obtaining a smooth transition from oneuncovered insulation zone to the connection zone.

After having determined the material removal that achieves the desiredgeometry, the robot controller 46 then controls the robot 42 to removethe material for obtaining the desired shape, step 36. In this case itis possible that the second tool 48 is reused, as is shown in FIG. 7 .Here also the angle α is shown.

Thereafter the robot 42 applies further insulation 58 around the cones50 and the additional insulation layer 52 in the connecting section CZso that the insulation is aligned with insulation of the cable, step 38.This further insulation is with advantage of the same type as theinsulation used in the second insulation layer 14 of the cable, i.e.,the same material as is present in the cones 50. This may be done usingthe third tool 48 and winding strips of insulation round the cones andsemiconductive insulation. This is schematically shown in FIG. 8 .

Thereafter may follow a heat treatment of the applied insulation as wellas the application of a ground layer and sheath. In all these lattersteps the same robot may be used.

It can in this way be seen that the desired geometry is obtained in aprecise way where there are smooth transitions between the cones and theadditional insulation layer and smooth or corrugated surfaces. Therebythe electric fields will be smooth and the reliability of the jointincreased. Moreover, the production is fast since the same robot may beused for the different operations. There is thereby no need for movingthe cables between differed machines.

Here it may also be mentioned that although different tools weredescribed above, it is possible to use a multipurpose tool havingcutting, smoothing and winding functionality, in which case the speedmay be increased even further.

There are a number of variations that are possible apart from thosealready discussed. It is for instance possible that the initial step ofremoving material and forming of cones are not performed using a robot,but instead are carried out in one or two dedicated machines. It is alsopossible that the applying of ordinary insulation above the cones andthe semiconductive insulation layer is performed in a dedicated machine.

It is also possible that the application of the semiconductiveinsulation layer in the connection zone is performed in a separatemachine.

It is thus possible that only the measuring and the removal of materialin order to obtain a desired shape are actually performed by the robot.

Another possible variation is that the semiconductive insulation beingapplied is not being wound as strips. It may be applied as a number ofblocks that fit into each other when being placed around the connectedconductors.

The robot controller may be implemented as a processor with associatedprogram memory comprising computer instructions for implementing itsfunctionality.

The robot controller may therefore be provided in the form of aprocessor with associated program memory including computer program codefor performing its functionality. It may also be provided in the form ofa digital signal processor (DSP), Application Specific IntegratedCircuit (ASIC) or Field-Programmable Gate Array (FPGA).

A computer program may also be a computer program product, for instancein the form of a computer readable storage medium or data carrier, likea CD ROM disc or a memory stick, carrying a computer program with thecomputer program code, which will implement the functionality of theabove-described robot controller when being loaded into a processor. Onesuch computer program product in the form of a CD ROM disc 60 with theabove-mentioned computer program code 62 is schematically shown in FIG.9 .

A computer program product may also be a program provided via a serverand downloaded therefrom to the robot controller.

While the invention has been described in connection with what ispresently considered to be most practical and preferred embodiments, itis to be understood that the invention is not to be limited to thedisclosed embodiments, but on the contrary, is intended to cover variousmodifications and equivalent arrangements. Therefore, the invention isonly to be limited by the following claims.

The invention claimed is:
 1. An arrangement for improving properties of a joint between two cable ends, the arrangement comprising: a robot with a robot controller, the robot controller being configured to, control the robot to obtain two cable ends, conductors of which are uncovered and joined in a connection zone (CZ), each cable end also having an uncovered insulation zone (UIZ1, UIZ2) including uncovered insulation formed as a cone adjacent the uncovered conductor, control the robot to cover the joined conductors with a layer of additional insulation, control the robot to measure the layer of additional insulation and the cones, determine a geometry of cones and the layer of additional insulation based on measurements, determine a deviation of the geometry from a desired geometry of the cones and the layer of additional insulation, where the desired geometry includes a smooth transition from the uncovered insulation zones to the connection zone, determining, based on the deviation determination, material to be removed from the cones and the layer of additional insulation achieving the desired geometry, and control the robot to remove said material from the cones and the additional layer of insulation in order to obtain a joint with improved properties.
 2. The arrangement according to claim 1, wherein the geometries of both cones are considered in the determining of material to be removed for obtaining a smooth transition from each uncovered insulation zone to the connection zone.
 3. The arrangement according to claim 1, wherein the desired geometry includes an angle (α) between a cone surface and a longitudinal axis (A) through the conductor and the robot controller, when controlling the robot to remove material is further configured to control the robot to retain the angle during the removal.
 4. The arrangement according to claim 1, wherein in the desired geometry each cone has a wall with a thickness that decreases towards the connection zone (CZ) and, in the uncovered insulation zone, the thickness of the cone wall closest to the connection zone is the same as the thickness of the additional layer of insulation at the point where it is closest to said uncovered insulation zone.
 5. The arrangement according to claim 1, wherein the desired geometry includes a smooth surface of the cones and the additional layer of insulation and the robot controller when controlling the robot to lower a level of the surface so that holes disappear.
 6. The arrangement according to claim 1, wherein the desired geometry includes corrugations on the cones and/or the layer of additional insulation.
 7. The arrangement according to claim 2, wherein the desired geometry includes an angle (α) between a cone surface and a longitudinal axis (A) through the conductor and the robot controller, when controlling the robot to remove material is further configured to control the robot to retain the angle during the removal.
 8. The arrangement according to claim 2, wherein in the desired geometry each cone has a wall with a thickness that decreases towards the connection zone (CZ) and, in the uncovered insulation zone, the thickness of the cone wall closest to the connection zone is the same as the thickness of the additional layer of insulation at the point where it is closest to said uncovered insulation zone.
 9. A computer program product for improving properties of a joint between two cable ends, the computer program product comprising: a non-transitory computer-readable storage medium; and a computer program code stored on the non-transitory computer-readable storage medium and configured to, when run in a robot controller for a robot, cause the robot controller to: control the robot to obtain two cable ends, conductors of which are uncovered and joined in a connection zone (CZ), each cable end also having an uncovered insulation zone (UIZ1, UIZ2) including uncovered insulation formed as a cone adjacent the uncovered conductor, control the robot to cover the joined conductors with a layer of additional insulation, control the robot to measure the layer of additional insulation and the cones, determine a geometry of the cones and the layer of additional insulation based on measurements, determine a deviation of the geometry from a desired geometry of the cones and the layer of additional insulation, where the desired geometry includes a smooth transition from the uncovered insulation zones to the connection zone, determine, based on the deviation determination, material to be removed from the cones and the layer of additional insulation achieving the desired geometry, and control the robot to remove said material from the cones and the additional layer of insulation in order to obtain a joint with improved properties. 